Extended identity based multi-signcryption scheme with public verifiability

Signcryption effectively accomplish encryption and signature procedure in a single logical step to acquire confidentiality, non-repudiation at minimum computational and communication overhead as compared to traditional scheme. In some applications, multiple senders authentic a message or document without revealing it by applying multiple signatures on it. It is not efficient to perform signcryption by each signer individually as unsigncryption cost is high. An alternative to reduce cost is multi signcryption. Numerous researchers worked on signcryption schemes to achieve security goals such as – confidentiality, non-repudiation, integrity, unforeability, forward secrecy and public verification. But none has provide solution to private key exposure. The biggest threat to the security is private key exposure and One time Pad (OTP) attack. With the increasing number of users, the threat is increasing on the low computation devices such as mobile phones, which requires private key for signature. Public key is derived from the identity of the user, if anyone comes to know corresponding private key can store the message and perform replay attack. In this paper we presented a scheme to reduce the threats caused by private key exposure, replay attack and OTP attack. According to us this is first ID based multi-signcryption with private key updation at a time period t.